How to use Postgres JSONB datatype with JPA?

Edit: I see now that this is pretty much Hibernate dependent. But perhaps you can find something similar for EclipseLink.

I'll just add what I have as an answer, it originates from another SO answer but whatever. This will map jsonb to JsonObject of Google gson, but you can change it to something else if needed. To change to something else, change nullSafeGet, nullSafeSetand deepCopy methods.

public class JsonbType implements UserType {

    @Override
    public int[] sqlTypes() {
        return new int[] { Types.JAVA_OBJECT };
    }

    @Override
    public Class<JsonObject> returnedClass() {
        return JsonObject.class;
    }

    @Override
    public boolean equals(final Object x, final Object y) {
        if (x == y) {
            return true;
        }
        if (x == null || y == null) {
            return false;
        }
        return x.equals(y);
    }

    @Override
    public int hashCode(final Object x) {
        if (x == null) {
            return 0;
        }

        return x.hashCode();
    }

    @Nullable
    @Override
    public Object nullSafeGet(final ResultSet rs,
                              final String[] names,
                              final SessionImplementor session,
                              final Object owner) throws SQLException {
        final String json = rs.getString(names[0]);
        if (json == null) {
            return null;
        }

        final JsonParser jsonParser = new JsonParser();
        return jsonParser.parse(json).getAsJsonObject();
    }

    @Override
    public void nullSafeSet(final PreparedStatement st,
                            final Object value,
                            final int index,
                            final SessionImplementor session) throws SQLException {
        if (value == null) {
            st.setNull(index, Types.OTHER);
            return;
        }

        st.setObject(index, value.toString(), Types.OTHER);
    }

    @Nullable
    @Override
    public Object deepCopy(@Nullable final Object value) {
        if (value == null) {
            return null;
        }
        final JsonParser jsonParser = new JsonParser();
        return jsonParser.parse(value.toString()).getAsJsonObject();
    }

    @Override
    public boolean isMutable() {
        return true;
    }

    @Override
    public Serializable disassemble(final Object value) {
        final Object deepCopy = deepCopy(value);

        if (!(deepCopy instanceof Serializable)) {
            throw new SerializationException(
                    String.format("deepCopy of %s is not serializable", value), null);
        }

        return (Serializable) deepCopy;
    }

    @Nullable
    @Override
    public Object assemble(final Serializable cached, final Object owner) {
        return deepCopy(cached);
    }

    @Nullable
    @Override
    public Object replace(final Object original, final Object target, final Object owner) {
        return deepCopy(original);
    }
}

To use this, do:

public class SomeEntity {

    @Column(name = "jsonobject")
    @Type(type = "com.myapp.JsonbType") 
    private JsonObject jsonObject;

In addition, you need to set your dialect to indicate that JAVA_OBJECT = jsonb:

registerColumnType(Types.JAVA_OBJECT, "jsonb");

I think I found an analogy to Hibernate's UserType for EclipseLink.

http://www.eclipse.org/eclipselink/documentation/2.6/jpa/extensions/annotations_ref.htm#CHDEHJEB

You have to make a class that implements org.eclipse.persistence.mappings.converters.Converter and does the conversion for you, then use the @Convert annotation on every field where you are using that type.

For anyone looking for a Mysql solution with the JSON column type, here it is. FWIW I am using EclipseLink but this is a pure JPA solution.

@Column(name = "JSON_DATA", columnDefinition="JSON")
@Convert(converter=JsonAttributeConverter.class)
private Object jsonData;

and

@Converter
public class JsonAttributeConverter implements AttributeConverter <Object, String>
{

    private JsonbConfig cfg = new JsonbConfig().withFormatting(true);

    private Jsonb jsonb = JsonbBuilder.create(cfg);
    
    @Override
    public String convertToDatabaseColumn(Object object)
    {      
        if (object == null) return null;

        return jsonb.toJson(object);
    }

    @Override
    public Object convertToEntityAttribute(String value)
    {
        if (value == null) return null;

        return jsonb.fromJson(value, value.getClass());
    }

}

@Column(columnDefinition = "jsonb")
@JdbcTypeCode(SqlTypes.JSON)
private String columnYouSetAsJsonb; // Replace "columnYouSetAsJsonb" with the appropriate field/column name

This is the simplest way I have found to set a field in the Entity class. It works well for me for saving and querying.

I don't have much time to investigate how it is implemented. It would be nice if someone else explain how it works.